Differences in metabolism, placental transfer and fetal binding of teratogens are under investigation. Fetal outcome from prolonged gestation by delay of blastocyst implantation (with phenothiazines) and reinitiation of delayed implantation (with estrogens) are being studied. Animal models are being developed to evaluate the normal and abnormal primary palate formation. For this purpose, radiation, cyclophosphamide, and cadmium are being used. The different pathways, by which these agents induce clefts of the primary palate are under investigation. Among other objectives is the development of an in vitro system for direct manipulation of rodent embryos across the critical period of primary palate development. This system will be used to investigate the role of cations (zinc, magnesian iron, cadmium and lead) in the formation of primary palate. Studies of fetal binding of teratogens, especially of the benzhydrilpiperazine are continuing. The most recent results indicate that norchlorcyclizine (Nor.cc), a major teratogenic metabolite of chlorcyclizine, alters acid mucopolysaccharide (AMPS) metabolism in palatal shelves of rat embryos just prior to rotation. Furthermore, experiments suggest that Nor.cc altered the degradation rather than the synthesis of AMPS in palatal tissue.